1. Field of the Invention
The handling of radioactive wastes, and more specifically the removal and concentration of radioactive tritium from the water used to cool a nuclear reactor.
2. Brief Description of the Prior Art
Tritium is a radioactive isotope of hydrogen. A small quantity of the water used to cool nuclear reactors is converted by radiation to tritiated water, i.e., HTO and T.sub.2 O. It is desirable to remove the tritiated water from the normal water so that it can be either safely stored until its radioactivity decays, or effectively utilized for purposes such as fusion power. But, tritiated water is chemically and physically similar to normal water, and mixed with such a large quantity of normal water in a reactor cooling system, that excessive quantities of reactant material and/or energy are required to separate the tritium according to all prior art methods. Typical reactors now being designed and built have closed loop water cooling systems holding more than 97,000 gallons of water. A distribution of only 0.057 grams of tritium in that 97,000 gallons of cooling water will provide a potentially dangerous 550 Ci radiation level, and should be removed.
It is well known that tritium interacts chemically with many other materials, and it has been suggested to remove tritium from reactor cooling water by chemical interaction. More specifically, it has been suggested to react the cooling water with calcium carbid to produce tritiated acetylene which can be readily polymerized into a low volume solid. But, calcium carbide also reacts with normal water to produce normal acetylene. That method would therefore require impractically large quantities of calcium carbide and primarily convert normal water into polyacetylene. Approximately 1.4 million pounds of calcium carbide would be needed for just a single treatment of a 97,000 gallon cooling system.
It has also been suggested to remove tritium from reactor cooling water by first electrolyzing the water to separate oxygen, then separating the bulk of hydrogen from tritium by a substance such as vanadium hydride, and finally reacting the tritium and hydrogen with zirconium or other tritium-fixing material to form a low volume tritiated solid. The primary drawback of this process is that excessive energy would be required to electrolyze the large quantity of cooling water in present reactors.